The proliferation of data hungry wireless applications is driving the demand for higher power and bandwidth efficiency in emerging wireless transceivers. Two recent technological trends offer synergistic opportunities for meeting the increasing demands on wireless capacity: i) multiple-input, multiple-output (MIMO) systems that exploit multi-antenna arrays for higher capacity by simultaneously multiplexing multiple data streams, and ii) millimeter (mm) wave (mm-wave) communication systems, operating in the 60-100 gigahertz (GHz) band that provides larger bandwidths. A key advantage of mm-wave systems, and very-high frequency systems in general, is that they offer high-dimensional MIMO operation with relatively compact array sizes. In particular, there has been significant recent interest in mm-wave communication systems for high-rate (1-100 gigabit per second (Gb/s)) communication over line-of-sight (LoS) channels. Two competing designs dominate the state-of-the-art: i) traditional systems that employ continuous aperture “dish” antennas and offer high power efficiency, but no spatial multiplexing gain, and ii) MIMO systems that use discrete antenna arrays to offer a higher multiplexing gain, but suffer from power efficiency.